This invention relates to compounds that contain both vinyl silane functionality and epoxy functionality and that can be used as adhesion promoters or curable compositions.
Adhesive compositions are used in the fabrication and assembly of semiconductor packages and microelectronic devices, such as in the bonding of integrated circuit chips to lead frames or other substrates, and the bonding of circuit packages or assemblies to printed wire boards. Lead frames can be fabricated of 42Fe/58Ni alloy (Alloy 42), copper, or silver- or palladium-coated copper, and wire boards of ceramic or laminate, and adhesives that in general have good performance may be deficient when used on one or more of these substrates.
The addition of adhesion promoters to the adhesive compositions or the use of curable resins that contain adhesion promoting capability as the adhesive would serve to correct this deficiency.
In one embodiment, this invention relates to compounds that contain both vinyl silane functionality and epoxy functionality. In another embodiment, this invention is a curable composition, such as an adhesive, coating, or encapsulant composition, containing those compounds.
The compounds of this invention contain at least one epoxy functionality and at least one vinyl silane functionality. In general, these compounds can be prepared by the reaction of a glycidol or a glycidyl ether polyol with a vinyl silane. Suitable vinyl silanes include trivinylchlorosilane, methyl vinyl dichlorosilane, diphenyl vinyl chlorosilane and vinyl trichlorosilane.
In another embodiment, this invention is a curable composition, such as an adhesive, coating, encapsulant or sealant, containing the inventive compounds. The curable composition can be in the form of a paste prepared by standard blending or milling techniques, or can be a film prepared by film forming techniques as known in the art. The curable composition will include optionally a curing agent, and optionally a filler.
The inventive epoxy/vinyl silane compounds can be the main component in the curable composition or can be added as an adhesion promoter to another curable resin. When used as an adhesion promoter, the amount of the epoxy/vinyl silane compound used in the curable composition will be an effective amount to promote adhesion and, in general, an effective amount will range from 0.005 to 20.0 percent by weight of the formulation.
Examples of curable resins for use as the main component other than the inventive vinyl silanes include epoxies, electron donor resins (for example, vinyl ethers, thiol-enes, and resins that contain carbon to carbon double bonds attached to an aromatic ring and conjugated with the unsaturation in the aromatic ring, such as compounds derived from cinnamyl and styrenic starting compounds), and, electron acceptor resins (for example, fumarates, maleates, acrylates, and maleimides).
Suitable curing agents are thermal initiators and photoinitiators present in an effective amount to cure the composition. In general, those amounts will range from 0.5% to 30%, preferably 1% to 20%, by weight of the total organic material (that is, excluding any inorganic fillers) in the composition. Preferred thermal initiators include peroxides, such as butyl peroctoates and dicumyl peroxide, and azo compounds, such as 2,2xe2x80x2-azobis(2-methyl-propanenitrile) and 2,2xe2x80x2-azobis(2-methyl-butanenitrile). A preferred series of photoinitiators is one sold under the trademark Irgacure by Ciba Specialty Chemicals. In some formulations, both thermal initiation and photoinitiation may be desirable: the curing process can be started either by irradiation, followed by heat, or can be started by heat, followed by irradiation. In general, the curable compositions will cure within a temperature range of 70xc2x0 C. to 250xc2x0 C., and curing will be effected within a range of ten seconds to three hours. The actual cure profile will vary with the components and can be determined without undue experimentation by the practitioner.
The formulations may also comprise nonconductive or thermally or electrically conductive fillers. Suitable conductive fillers are carbon black, graphite, gold, silver, copper, platinum, palladium, nickel, aluminum, silicon carbide, boron nitride, diamond, and alumina. Suitable nonconductive fillers are particles of vermiculite, mica, wollastonite, calcium carbonate, titania, sand, glass, fused silica, fumed silica, barium sulfate, and halogenated ethylene polymers, such as tetrafluoroethylene, trifluoro-ethylene, vinylidene fluoride, vinyl fluoride, vinylidene chloride, and vinyl chloride. If present, fillers generally will be in amounts of 20% to 90% by weight of the formulation.
The following Examples disclose a synthetic procedure used to make the vinyl silane/epoxy compounds disclosed in this specification, and the performance of representative samples in curable compositions.